09/16/2011

White Sands National Monument

Visitors who find White Sands National Monument otherworldly are spot-on, particularly if the other world they’re imagining is Mars. Aerodynamic ridges called yardangs, found abundantly on the Red Planet, jut from southern New Mexico’s desert floor like ship bows. These gale-scoured forms seem to gamely plow into the unremitting spring winds, always from the southwest, but the cemented gypsum is quite stationary. It’s the region’s 4.5 billion tons of silky soft sand—composing the world’s largest gypsum dunefield—that is gently shooshing forward, dozens of feet each year.

Flora and fauna have apparently fared better here than on our planetary neighbor, but residency remains restricted to the entrepreneurial. In this constantly shifting landscape, some plants have learned to outmaneuver the dunes. When the soaptree yucca (pictured above) begins to be buried, it periscopes its stem, up to a foot a year, to keep its leaves above the encroaching sand. The skunkbush sumac one-ups the yucca, both extending its stems and using its roots to cling to a clump of sand; when the rest of the dune moves on, the plant remains on a solidified pedestal. This hardened, shaded gypsum then becomes an oasis for the desert’s beleaguered animals: The kit fox, for one, carves its den into the stabilized sand.

Other animals beat the heat with radical moisture-saving methods: The kangaroo rat stores food in external cheek pouches to avoid losing water from its mouth while foraging. To keep cool (and camouflaged from predators) the Apache pocket mouse and the bleached earless lizard are white as the sand. The spadefoot toad here is pale, too, but since the inhospitable desert is even more so to amphibians, it also has to be quick, sexually. The spadefoot lives underground until it hears the summer thunder, its cue to leap to a freshly formed pond for toady love. The fertilized eggs hatch just 20 hours later—faster than any other North American frog or toad’s—and rapidly mature into adults, which then hunker down in the damp sand to patiently await the next season’s storms.

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